My experience has been that they call at midnight (or whenever the RAP starts) if you don't acknowledge the trip during the 9 hours prior to being on call. You still have 10 hours of rest before you are required to report. Sometimes I am unable to check my schedule until my RAP starts and that's perfectly fine. 9 hours prior is the latest they can add flying, not when you must check it. Crew scheduling is not required to call though, so if you have to commute to base and can't during the first 10 hours it's on you to check and show for a trip. However, if you check at 9 hours prior and there's nothing, then you don't need to check again, just wait for contact.